ISO 19403-4:2024 PDF

Overview

ISO 19403-4:2024 specifies an optical test method to determine the polar and dispersive fractions of a liquid’s surface tension by measuring an interfacial tension with a reference liquid. Using pendant or ascending drops analyzed by drop contour imaging, the method derives polar/dispersive components (e.g., via Owens–Wendt–Rabel–Kaelble or Wu approaches) to characterize liquid coatings and other fluids where conventional measurements may be affected by drying or surface activity.

Keywords: ISO 19403-4, wettability, surface tension, polar and dispersive fractions, interfacial tension, drop contour analysis, pendant drop.

Key topics and technical requirements

• Principle: Create a pendant/ascending drop of the test liquid inside an optical cell filled with a reference liquid and compute interfacial tension from the drop shape using the Young–Laplace equation (see ISO 19403-1).
• Apparatus: State-of-the-art drop contour analysis system with digital imaging, dosing unit (needle OD 0.5–2.5 mm), and an optical cell with plane parallel walls (wall thickness